refactor: migrate to Swift 6 language mode

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ env:
 jobs:
   build:
     name: Build & Analyze
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - uses: actions/checkout@v6
 
@@ -51,7 +51,7 @@ jobs:
 
   lint:
     name: SwiftLint
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - uses: actions/checkout@v6
       - name: Install SwiftLint

.github/workflows/codeql.yml

@@ -25,7 +25,7 @@ env:
 jobs:
   analyze:
     name: Analyze (Swift)
-    runs-on: macos-15
+    runs-on: macos-26
     permissions:
       actions: read
       contents: read

.github/workflows/release.yml

@@ -18,7 +18,7 @@ env:
 jobs:
   build-release:
     name: Build unsigned .app
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - uses: actions/checkout@v6
 

Maple.xcodeproj/project.pbxproj

@@ -420,7 +420,7 @@
 				SWIFT_DEFAULT_ACTOR_ISOLATION = MainActor;
 				SWIFT_EMIT_LOC_STRINGS = YES;
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 			};
 			name = Debug;
 		};
@@ -456,7 +456,7 @@
 				SWIFT_DEFAULT_ACTOR_ISOLATION = MainActor;
 				SWIFT_EMIT_LOC_STRINGS = YES;
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 			};
 			name = Release;
 		};
@@ -476,7 +476,7 @@
 				SWIFT_APPROACHABLE_CONCURRENCY = YES;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TEST_HOST = "$(BUILT_PRODUCTS_DIR)/Maple.app/$(BUNDLE_EXECUTABLE_FOLDER_PATH)/Maple";
 			};
 			name = Debug;
@@ -497,7 +497,7 @@
 				SWIFT_APPROACHABLE_CONCURRENCY = YES;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TEST_HOST = "$(BUILT_PRODUCTS_DIR)/Maple.app/$(BUNDLE_EXECUTABLE_FOLDER_PATH)/Maple";
 			};
 			name = Release;
@@ -516,7 +516,7 @@
 				SWIFT_APPROACHABLE_CONCURRENCY = YES;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TEST_TARGET_NAME = Maple;
 			};
 			name = Debug;
@@ -535,7 +535,7 @@
 				SWIFT_APPROACHABLE_CONCURRENCY = YES;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TEST_TARGET_NAME = Maple;
 			};
 			name = Release;

Maple/Models/GitModels.swift

@@ -133,7 +133,7 @@ struct DiffHunk: Identifiable, Sendable {
 /// One file's diff: the raw preamble lines (`diff --git`, `index`, `---`, `+++`)
 /// grouped together with that file's hunks. Preserving the preamble is what
 /// lets us round-trip a subset of hunks back into `git apply --cached`.
-struct DiffFile: Identifiable, Sendable {
+nonisolated struct DiffFile: Identifiable, Sendable {
     let id = UUID()
     let path: String?
     let preamble: [String]

Maple/Services/DiffParser.swift

@@ -8,8 +8,9 @@
 import Foundation
 
 /// Parses raw `git diff` / `git show` output into structured `DiffFile` /
-/// `DiffLine` representations.
-enum DiffParser {
+/// `DiffLine` representations. Nonisolated because parsing is pure
+/// value-to-value work that must run in any actor's isolation domain.
+nonisolated enum DiffParser {
 
     /// Structured view: one entry per file, each with its preamble preserved so
     /// a patch can be reconstructed for a subset of hunks later.

Maple/Services/FileWatcher.swift

@@ -11,7 +11,7 @@ import Observation
 @Observable
 final class FileWatcher {
 
-    /// Callback fired (on the main thread) when watched directory changes.
+    /// Callback fired on the main actor when the watched directory changes.
     var onChange: (() -> Void)?
 
     private var sources: [DispatchSourceFileSystemObject] = []
@@ -108,7 +108,7 @@ final class FileWatcher {
         )
     }
 
-    deinit {
+    isolated deinit {
         stop()
     }
 }

README.md

@@ -4,7 +4,7 @@
 
 [![CI](https://github.com/poolcamacho/Maple/actions/workflows/ci.yml/badge.svg)](https://github.com/poolcamacho/Maple/actions/workflows/ci.yml)
 [![Platform](https://img.shields.io/badge/platform-macOS%2014%2B-lightgrey)](https://www.apple.com/macos/)
-[![Swift](https://img.shields.io/badge/Swift-5-orange)](https://swift.org)
+[![Swift](https://img.shields.io/badge/Swift-6-orange)](https://swift.org)
 [![License: MIT](https://img.shields.io/github/license/poolcamacho/Maple)](LICENSE)
 [![Stars](https://img.shields.io/github/stars/poolcamacho/Maple?style=flat)](https://github.com/poolcamacho/Maple/stargazers)
 [![Forks](https://img.shields.io/github/forks/poolcamacho/Maple?style=flat)](https://github.com/poolcamacho/Maple/network/members)
@@ -46,7 +46,7 @@ Most Git GUIs on macOS are Electron based, locked behind a subscription, or over
 ## Requirements
 
 - macOS 14.0+ (Apple Silicon recommended, Intel supported)
-- Xcode 16+
+- Xcode 26+ (Swift 6.3 toolchain; required for `isolated deinit`)
 - Git installed (ships with Xcode Command Line Tools)
 
 ## Getting started